So far I belive ghengis khan is a genius. At a young age he is able to make smart military decisions and is able to take on the role of a lear. Although yes he is a Physocopath and killed many people he was able to bring together one of the largest empires of all time. And yes you killed a lot of people to do so but it takes brains to be able to do that

Material life in the Carolingian countryside

Power on an early medieval manor seemed to be judged by the amount of material goods you had. The lords of the manors were in control of the estate and the people working there. All of the people had a job to do and they were required to give a portion of their time and whatever they produced to The Lord. This meant a that The Lord didn't have to work (so wealthy he doesn't have to do anything) and the serfs and peasants did. The reason they gave there goods to The Lord is because he provided them protection and a place to farm. This meant lords had a lot of stuff and the serfs had very little. The stewards job is to keep track of all the goods a lord owns much like money as well as all of the goods the serfs are required to give to The Lord, again much like money. So it is safe to assume that during this time power was determined by the amount of stuff you had.

India and Europe decentralization, comparison map